Wireless communication devices often need to simultaneously operate in more than one wireless communication network. For example, a wireless communication device may need to simultaneously operate in a Private Area Network Basic Service Set (PAN BSS) and a Wireless Local Area Network Basic Service Set (WLAN BSS). The networks typically implement one or more of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard family of communications protocols, such as 802.11b, 802.11d, 802.11h or other variants.
In order to be perceived as simultaneously operating in both networks, the virtual Media Access Controls (MACs) of the wireless communication devices need to periodically operate in each of the networks. This involves leaving a first network for a second network while notifying the cell of its absence from the first network for a period of time. If the device is an Access Point (AP) for the network, it is assumed to always be available to the clients of the network. Therefore, if the AP is not available, the clients may disadvantageously assume that the AP has dropped out and the clients may commence a roaming procedure for a replacement AP.
All virtual MACs share the same physical layer (PHY), but may operate on different channels for various reasons, such as better spectrum/bandwidth utilization for multiple PANs. Sharing a common PHY requires the virtual MACs to operate in Time Division Multiple Access (TDMA) mode for multiple channel operation, wherein a wireless Network Interface Card (NIC) switches from one virtual MAC to another virtual MAC in a certain order.
When a virtual MAC is implementing an AP and working in TDMA mode, the virtual MAC will be available on the operating channel for only part of the time. When another station scans the channel for available networks, the station uses an active scan mode by sending a probe request and waiting for a probe response. The probe request can be sent on the channel even when the virtual MAC AP does not reside on the channel. However, this results in the drawback of the station taking longer to detect the AP or not detecting the virtual MAC AP in the channel at all.
Skilled addressees will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the relative dimensions of some of the elements in the figures may be distorted to help improve understanding of embodiments of the present invention.